1. Field of the Invention
The present invention relates to a seal ring which is incorporated in, for example, a rolling bearing and relates to a sealing apparatus so-called a pack seal.
The present invention, more particularly, relates to a seal ring into which a rotation detecting sensor is incorporated, a sealing apparatus into which a rotation detecting apparatus composed of the above sensor and a pulsar ring whose rotation is detected by the sensor, and a bearing apparatus having them.
2. Description of the Related Art
Both a magnetic sensor and a pulsar ring provided with N poles and S poles alternatively in a peripheral direction are incorporated as a rotation detecting device into, for example, a bearing apparatus for an axle of an automobile, and they are used for detecting a wheel speed when anti-locking brake control is made.
The present inventors suggest a structure that such a rotation detecting device is integral with a sealing apparatus called as a pack seal.
The seal pack of this suggestion has an outer diameter side seal ring fixed to an inner periphery of an outer ring of a rolling bearing, and an inner diameter side seal ring fixed to an outer periphery of an inner ring.
The magnetic sensor is attached to an inner diameter side of the outer diameter side seal ring. The pulsar ring is attached to an outer diameter side of the inner diameter side seal ring so as to face the magnetic sensor in a radial direction.
In this case, the magnetic sensor is attached to an inner periphery of an annular body of the outer diameter side seal ring by a mold using a resin material. The resin material is formed integrally with or bonded to the annular body of the outer diameter side seal ring so as to become a outer case which covers a periphery of the sensor.
Such a structure is provided because the annular body of the outer diameter side seal ring is press-fitted into an inner peripheral surface of an outer ring or the like so that the outer diameter side seal ring is attached firmly to the outer ring.
However, in the case of the structure that the magnetic sensor is attached to the inner periphery of the annular body of the outer diameter side seal ring by the mold, since a difference in coefficient of linear expansion between the annular body of the outer diameter side seal ring and the outer case is large, after the outer case is formed, it contracts. As a result, a gap is easily generated on a boundary surface between the inner periphery of the annular body of the outer diameter side seal ring and the outer case.
When such a gap is generated, water which splashes on the seal ring from the outside easily penetrates from the gap into the bearing, and this might cause deterioration of the bearing performance such that lubricant inside the bearing is deteriorated.